Fucking shitcunts. I have no idea what to suggest, other than getting on to every local and national disability / benefits advice type service until someone helps (which I'm sure you've already tried), but I really hope you get this sorted.
Worst case scenario, I think you're allowed to put in a new claim if you run out of appeal options? Would mean you lose out on backpay though and you're not guaranteed to get a different decision
E2a - was your request for a UT appeal specifically on the grounds that the FTT had made an error of law?